Combustion tests and gaseous emissions of olive mill solid wastes pellets (olive pomace (OP), and olive pits (OPi)) were carried out in an updraft counter-current fixed bed reactor. Along the combustion chamber axis and under a constant primary air flow rate, the bed temperatures and the mass loss rate were measured as functions of time. Moreover, the gas mixture components such as O2, organic carbon (Corg), CO, CO2, H2O, H2, SO2, and NOx (NO + NO2) were analyzed and measured. The reaction front positions were determined as well as the ignition rate and the reaction front velocity. We have found that the exhaust gases are emitted in acceptable concentrations compared to the combustion of standard wood pellets reported in the literature (EN 303-5). It is shown that the bed temperature increased from the ambient value to a maximum value ranging from 750 to 1000 °C as previously reported in the literature. The results demonstrate the promise of using olive mill solid waste pellets as an alternative biofuel for heat and/or electricity production.
Batch biochemical methane potential (BMP) assays to evaluate the methane yield of biogas substrates such as energy crops are usually carried out with undiluted inoculum. A BMP assay was performed on two energy crops (green cuttings and grass silage). Anaerobic digestion was performed both with and without supplementation of three commercial additives containing trace metals in liquid, solid or adsorbed form (on clay particles). In order to reveal positive effects of trace metal supplementation on the methane yield, besides undiluted inoculum, 3-fold and 10-fold dilutions of the inoculum were applied for substrate digestion. Diluted inoculum variants were supplemented with both mineral nutrients and pH-buffering substances to prevent a collapse of the digestion process. As expected, commercial additives had no effect on the digestion process performed with undiluted inoculum, while significant increases of methane production through trace element supplementation could be observed on the diluted variants. The effect of inoculum dilution may be twofold: (1) decrease in trace metal supplementation from the inoculum and (2) reduction in the initial number of bacterial cells. Bacteria require higher growth rates for substrate degradation and hence have higher trace element consumption. According to common knowledge of the biogas process, periods with volatile fatty acids accumulation and decreased pH may have occurred in the course ofanaerobic digestion. These effects may have led to inhibition, not only ofmethanogenes and acetogenes involved in the final phases of methane production, but also offibre-degrading bacterial strains involved in polymer hydrolysis. Further research is required to confirm this hypothesis.
Um zu klären, wie lange durch präferenziellen Transport in den Unterboden gelangte Herbizide dort persistieren, wird beispielhaft der mikrobielle Abbau des Herbizids Isoproturon am Ende von Makroporen/Wurmgängen in 80–100 cm Tiefe mit dem Abbau in der umgebenden Bodenmatrix verglichen. Dazu wurde eine Methode entwickelt, welche die Messung des Isoproturon‐Abbaus in Makroporen unter Feldbedingungen erlaubt. Nach Voruntersuchungen zur Optimierung von Applikation und Probennahme wurden im Einzugsgebiet des Weiherbachs (Kraichgau, SW Deutschland) auf einer überdachten Versuchsparzelle 55 Wurmgänge mit einer Tiefe von 80–100 cm mit Isoproturon beimpft. In Boden der Versuchsparzelle wurden parallel Bodenfeuchte und ‐temperatur kontinuierlich gemessen. Jeweils 5–6 der beimpften Wurmgänge wurden alle 8 Tage herauspräpariert und auf ihren Gehalt an Isoproturon untersucht, um die Kinetik des Abbaus zu ermitteln. Parallel erfolgte die Untersuchung des Abbaus von Isoproturon in der die Wurmgänge umgebenden Bodenmatrix im Labor. Die Ergebnisse der Feld‐ und Laborversuche zeigen, dass der mikrobielle Abbau von Isoproturon direkt am Ende der Wurmgänge mit einem DT‐50‐Wert von 15,6 d ähnlich schnell erfolgt wie im Oberboden. Bereits wenige Zentimeter vom Zentrum des Wurmgangs entfernt zeigte sich in der umgebenden Unterbodenmatrix innerhalb von 30 d kein Abbau von Isoproturon. Diese deutliche Zunahme der Persistenzzeit konnte durch die wesentlich geringere mikrobielle Aktivität in der umgebenden Bodenmatrix erklärt werden. Für das Schicksal eines Herbizids, welches durch präferenzielle Fließereignisse in den Unterboden gelangt ist, ist somit entscheidend, ob es aus der Makropore in die umgebende Bodenmatrix transportiert wird oder nicht, denn die Abbauraten im Unterboden nehmen bereits nach wenigen Zentimetern um etwa eine Größenordnung ab. Aussagen dieser Genauigkeit sind selbst mit hochauflösenden Prozessmodellen bestenfalls für extrem gut untersuchte Standorte ableitbar.
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